Article
Functional mapping of cortical language areas using paired-pulse and higher-frequent repetitive TMS
FunktionelleKartierung kortikaler Sprachareale mittels Doppelpuls- und hochfrequenter repetitiver TMS
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Published: | June 26, 2020 |
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Objective: During the last years, a lot of effort has been made to investigate the cortical distribution of language-relevant areas on the individual level. For language mapping with repetitive transcranial magnetic stimulation (rTMS) a stimulation frequency of 5-10 Hz is most commonly used. Nevertheless, this rTMS protocol still has some limitations like small number of evoked language errors. We, therefore, designed new TMS protocols using paired-pulse (pp) TMS as well as higher-frequent rTMS aiming at improved language mapping, i.e. evoking a higher number of language errors.
Methods: 20 healthy, right-handed subjects (w=11, 23 ± 3 years) were investigated using three different rTMS protocols:
- (i) 5 Hz rTMS,
- (ii) introductory pp followed by 32 Hz rTMS (pp + 32 Hz) and
- (iii) bursts of paired-pulses with a repetition rate of 32 Hz (32 Hz-pp).
TMS protocols were applied in a pseudo-randomized order during a picture naming task (picture-to-trigger interval: 0 ms) over the inferior frontal gyrus, primary motor cortex, supramarginal gyrus, angular gyrus, superior and middle temporal gyrus (as defined by fMRI).
Results: Overall, lowest error rates were found for the standard protocol of 5 Hz (15 ± 9 %, p<0.05, FDR-corrected). There was no significant difference between the standard and the 32 Hz-pp protocol (19 ± 11 %, p>0.1, FDR-corrected), whereas a significant higher number of errors could be evoked using the pp + 32 Hz protocol (27 ± 13 %).
Conclusion: We found promising results in terms of increased error rates especially when using combined pp- and rTMS for mapping of cortical language areas. In our series, the pp + 32 Hz protocol war clearly superior to the standard technique and should be further evaluated. Clinical studies are planned to demonstrate the validity of this improved language mapping protocol in patients. Moreover, train duration and picture-to-trigger interval may be optimized with regard to the location-dependent dynamics of cortical language processing.